Max Heart Rate Formula: Why 220 − Age Reads Low
Almost every heart-rate zone you have ever been given starts from one number: your maximum heart rate. Most apps and charts estimate it as 220 minus your age. For most adults over 30, that estimate is too low, and the error grows every year. Here is how the common formulas compare, what the difference does to a Norwegian 4x4 training zone, and how to find your real number.
Published September 19, 2026Last updated September 19, 2026By Archline Labs LLCEditorial methodology
The short answer
- 220 − age is a rule of thumb with no single study behind it. It underestimates measured max heart rate for most people over about 30.
- Tanaka (208 − 0.7 × age) and HUNT (211 − 0.64 × age) are both based on large sets of measured data and track real values better.
- Every age formula is off by about 10 bpm for an individual, in either direction. A max you have actually measured beats all of them.
- For the Norwegian 4x4, the error lands exactly where it matters: a max that reads low drags the whole 85–95% work zone down with it.
Where 220 − age came from
220 minus age is so familiar that it is easy to assume it came from a landmark study. It did not. In a 2002 review, Robergs and Landwehr traced the formula's history and found it was drawn from an informal fit to roughly eleven older references, mixing published research with unpublished compilations, rather than from original research designed to predict maximal heart rate. It was never published with an error estimate, and it was never validated across ages the way later equations were.
It survived because it is easy to do in your head. That is a real advantage on a gym wall chart, and a poor reason to set the intensity of a training program.
The three formulas compared
| Age | 220 − age | Tanaka 208 − 0.7 × age |
HUNT 211 − 0.64 × age |
|---|---|---|---|
| 30 | 190 | 187 | 192 |
| 40 | 180 | 180 | 185 |
| 50 | 170 | 173 | 179 |
| 60 | 160 | 166 | 173 |
| 70 | 150 | 159 | 166 |
The pattern is the important part. At 30 the three agree within a few beats. By 60, 220 − age sits 13 bpm below the HUNT estimate. By 70 the gap is 16 bpm. The error is not random noise that averages out; it points the same direction and grows with age.
Tanaka: 208 − 0.7 × age
Tanaka, Monahan and Seals published this equation in 2001 in the Journal of the American College of Cardiology, combining a meta-analysis of published studies with their own laboratory measurements in healthy adults. It is widely used and a clear improvement on 220 − age, particularly for older adults.
HUNT: 211 − 0.64 × age
The HUNT equation comes from Nes, Janszky, Wisløff, Støylen and Karlsen, published in 2013 in the Scandinavian Journal of Medicine & Science in Sports. The researchers measured maximal heart rate directly, in maximal exercise tests, in 3,320 healthy men and women across a wide age range from the HUNT Fitness Study in Norway. The equation's standard error of estimate is about 10.8 bpm, and the authors report that earlier prediction equations underestimated measured max heart rate in people older than 30.
There is a second reason this one matters for interval training. It comes from NTNU in Trondheim, the same institution and research community behind the Norwegian 4x4 research. When a protocol says "85–95% of maximum heart rate," it helps to estimate that maximum the way the people who developed the protocol measured it.
What the formula does to your 4x4 zone
NTNU's Cardiac Exercise Research Group prescribes the Norwegian 4x4 as four 4-minute intervals at 85–95% of maximum heart rate, with 3-minute active recoveries. Because the target is a percentage, any error in your estimated maximum carries straight through to the zone.
| Age | Zone from 220 − age | Zone from HUNT |
|---|---|---|
| 30 | 162–181 bpm | 163–182 bpm |
| 40 | 153–171 bpm | 157–176 bpm |
| 50 | 145–162 bpm | 152–170 bpm |
| 60 | 136–152 bpm | 147–164 bpm |
| 70 | 128–143 bpm | 141–158 bpm |
Consider a 60-year-old following a 220 − age zone of 136–152 bpm. They can finish all four intervals "in the zone" and still spend most of the session below the effort the protocol is designed around. Nothing looks wrong, because the app or watch confirms they hit the target. The target was simply set too low. This is the most useful practical reason to care which formula you use.
What no formula can tell you
- Any age formula describes a population, not you. With an error of about 10 bpm, two healthy 50-year-olds can have true maximums 20 bpm apart. Neither is abnormal.
- Fitness does not change your max much. A high max is not a sign of good fitness, and a low one is not a sign of poor fitness. It mostly reflects age and individual variation.
- Medications matter. Beta blockers and some other drugs lower maximal heart rate. If you take one, no age formula applies; ask your clinician how to set intensity.
- Wrist sensors lag in hard efforts. Optical heart rate is least accurate during rapid rises, which is exactly the start of a hard interval. A chest strap is more reliable for testing and for 4x4 work.
How to find your real max heart rate
The best estimate is a measured one. NTNU's Cardiac Exercise Research Group describes a practical field test built around the 4x4 itself:
- Warm up thoroughly, until you are sweating.
- Run two 4-minute hard intervals, uphill if you can, with easy recovery between.
- Start a third interval. After about two minutes, go as hard as you can until you are too exhausted to continue.
- The highest heart rate you record is close to your maximum. A chest strap gives the most trustworthy reading.
Only do a maximal test if you are healthy and used to hard exercise. If you have a heart condition, high blood pressure, symptoms during exercise, or any doubt, get medical clearance first; NTNU's advice is to see a doctor and, if needed, a supervised exercise test.
How Ramp4x4 sets your zone
Ramp4x4 is a guided Norwegian 4x4 app for iPhone and Apple Watch. It builds your work zone as 85–95% of your maximum heart rate and coaches every interval against it with live heart rate, voice cues and haptics.
- Your tested max comes first. Enter a measured maximum and Ramp4x4 uses it instead of any estimate.
- Resting heart rate is optional. If you know it, you can switch to heart-rate-reserve (Karvonen) targets, which account for a resting heart rate far from average.
- The age estimate uses HUNT. Since version 2.3, Ramp4x4 estimates your max with the HUNT equation instead of 220 − age. Existing users who relied on an age estimate are shown both zones side by side and asked before anything changes, and completed workouts keep the zone they were trained against.
You can try the numbers for your own age in the 4x4 heart-rate calculator.
Train the 4x4 against the right number
Ramp4x4 calculates your work and recovery zones, uses your tested max when you have one, and coaches every phase of the Norwegian 4x4 on iPhone and Apple Watch with live heart rate, haptics and voice.
Max heart rate FAQ
Is 220 minus age accurate?
Not very. The 220 minus age rule was never derived from a single study; it was drawn from a loose set of older references. Large studies that measured maximal heart rate directly, including the HUNT Fitness Study of 3,320 healthy Norwegian adults, found that it underestimates measured max heart rate for people over about 30, and the gap grows with age. At 60 it reads roughly 13 beats per minute low.
What is the most accurate max heart rate formula?
No formula is accurate for an individual; every age equation has an error of roughly 10 beats per minute either way. Among age equations, Tanaka (208 minus 0.7 times age) and the HUNT equation (211 minus 0.64 times age) both track measured values better than 220 minus age. For the Norwegian 4x4 specifically, HUNT is the natural choice because it was measured by the same NTNU research group whose protocol the 4x4 comes from. A max you have actually tested beats every formula.
What is the HUNT max heart rate formula?
Max heart rate = 211 minus 0.64 times age. It comes from Nes and colleagues, 2013, in the Scandinavian Journal of Medicine and Science in Sports, based on directly measured maximal heart rate in 3,320 healthy adults from the HUNT Fitness Study in Norway. The reported standard error of estimate is about 10.8 beats per minute.
How do I find my real max heart rate?
Measure it in a hard, well-warmed-up effort with a reliable heart-rate sensor, ideally a chest strap. NTNU's Cardiac Exercise Research Group describes one approach: warm up thoroughly, do two 4-minute hard intervals, then two minutes into a third, go as hard as you can until you cannot continue. The highest value you see is close to your maximum. Only do this if you are healthy and cleared for maximal exercise.
References
- Nes BM, Janszky I, Wisløff U, Støylen A, Karlsen T. Age-predicted maximal heart rate in healthy subjects: The HUNT Fitness Study. Scandinavian Journal of Medicine & Science in Sports. 2013;23(6):697–704. DOI: 10.1111/j.1600-0838.2012.01445.x.
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. Journal of the American College of Cardiology. 2001;37(1):153–156. DOI: 10.1016/S0735-1097(00)01054-8.
- Robergs RA, Landwehr R. The surprising history of the "HRmax = 220 − age" equation. Journal of Exercise Physiology Online. 2002;5(2):1–10.
- NTNU Cardiac Exercise Research Group. Exercise advice. Protocol description and maximal heart rate field test.
- Helgerud J, Høydal K, Wang E, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Medicine & Science in Sports & Exercise. 2007;39(4):665–671.